CN103954348A - Distributed optical fiber vibration sensing system based on differential pulse sequence - Google Patents
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 94
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Abstract
The invention discloses a distributed optical fiber vibration sensing system based on a differential pulse sequence. The distributed optical fiber vibration sensing system comprises a light source, a first coupler, first to Nth acoustic optical modulation devices, (N-1) delay optical fibers, a second coupler, an erbium-doped optical fiber amplifier, an optical filter, a three-port circulator, a long-distance sensing optical fiber, a third coupler, a photoelectric detector, a high-pass filter, a frequency mixer, a function generator, a low-pass filter and a data acquisition card. The distributed optical fiber vibration sensing system based on the differential pulse sequence can achieve measurement of a high-frequency vibration signal within a long-distance range and accurate position judgment and can reduce the system cost to certain extent.
Description
Technical field
The present invention relates to a kind of distributed optical fiber vibration sensing system, particularly a kind of distributed optical fiber vibration sensing system based on differential pulse sequence.
Background technology
Vibratory output is measured has potential applying value at engineering field, as safety monitorings such as monitoring structural health conditions, Aero-Space, petrochemical complex, electric system.Traditional vibration measurement method is as Mechanical measurement method, electrometric method, all have that sensitivity is low, volume is large, measurement range is subject to the problems such as amplifying device restriction, and traditional vibration measurement method can only carry out point measurement, in practice, be restricted, therefore develop high performance Vibration-Measuring System imperative.
Distributed Optical Fiber Sensing Techniques refers to along the external signal on optical fiber transmission path and in some way the light wave in optical fiber is constantly modulated, to realize, the continuous space of measured is measured in real time, optical fiber is light-conductive media, as sensing element, respond to extraneous vibration signal simultaneously.
The research of vibration sensing system based on optical fiber technology in prior art is very extensive, but the measurement of existing measurement means lower frequency when all existing vibration position accurately to measure, or the vibration survey of upper frequency but the lower problem of spatial resolution.In order to adapt to the demand of modern Large Infrastructure Projects health monitoring, certainly will to realize the measurement of high-frequency vibration signal in long distance range and accurate position judgment simultaneously, and will to a certain degree reduce system cost.
Summary of the invention
Embodiment of the present invention technical matters to be solved is, provides a kind of and realizes the measurement of high-frequency vibration signal in long distance range and accurate position judgment, and can reduce to a certain extent the distributed optical fiber vibration sensing system of system cost.
A kind of distributed optical fiber vibration sensing system based on differential pulse sequence provided by the present invention, for the vibration of designated space is carried out to sensing, the described distributed optical fiber vibration sensing system based on differential pulse sequence comprises:
Light source, the first coupling mechanism, first sound-optic modulator to the N acousto-optic modulator, (N-1) individual delay optical fiber, the second coupling mechanism, Erbium-Doped Fiber Amplifier (EDFA), optical filter, three port circulators, long-distance sensing optical fiber, the 3rd coupling mechanism, photodetector, Hi-pass filter, frequency mixer, function generator, low-pass filter and data collecting card, wherein N is more than or equal to 2 natural number, described long-distance sensing optical fiber is layed in tested designated space, described light source is connected with the input end light path of the first coupling mechanism, first of described the first coupling mechanism is connected with the first input end to N acousto-optic modulator respectively to N output terminal, (N+1) output terminal of described the first coupling mechanism is connected with the first input end of the second coupling mechanism, the output terminal of described first sound-optic modulator is connected with the first input end of the 3rd coupling mechanism, the output terminal of described second sound-optic modulator to the N acousto-optic modulator is corresponding to be respectively connected with the input end of (N-1) individual delay optical fiber, the output terminal of described (N-1) individual delay optical fiber is second being connected to N input end of corresponding and the 3rd coupling mechanism respectively, described the 3rd output terminal of coupling mechanism and the input end of Erbium-Doped Fiber Amplifier (EDFA) are connected, the output terminal of described Erbium-Doped Fiber Amplifier (EDFA) is connected with the input end of optical filter, the output terminal of described optical filter is connected with the input end of three port circulators, the multiplexing end of transmitting-receiving of described three port circulators is connected with the second input end of the second coupling mechanism, the output terminal of described three port circulators is connected with one end of long-distance sensing optical fiber, the output terminal of described the second coupling mechanism is connected with the output terminal of photodetector, the output terminal of described photodetector is connected with the input end of Hi-pass filter, the output terminal of described Hi-pass filter is connected with the first input end of frequency mixer, the second input end function generator of described frequency mixer is connected, described function generator is also connected with second sound-optic modulator with first sound-optic modulator, the output terminal of described frequency mixer is connected with the input end of low-pass filter, the output terminal of described low-pass filter is connected with data collecting card.
Wherein, described the first coupling mechanism is 1 * (N+1) coupling mechanism.
Wherein, described the 3rd coupling mechanism is N * 1 coupling mechanism.
In order further to improve the signal to noise ratio (S/N ratio) of the signal of the second coupling mechanism output, photodetector in the above-mentioned distributed optical fiber vibration sensing system based on differential pulse sequence is adopted as balance photodetector, described the second coupling mechanism is 2 * 2 coupling mechanisms, and two output terminals of described the second coupling mechanism are connected one by one with two input ends of balance photodetector.
In order further to improve the accuracy of the above-mentioned distributed optical fiber vibration sensing system based on differential pulse sequence, described function generator is consistent to the driving parameter of N acousto-optic modulator to first; The frequency of the cosine signal that the 3rd port of described function generator connection frequency mixer produces is 85MHz.
In order further to improve the accuracy of the above-mentioned distributed optical fiber vibration sensing system based on differential pulse sequence, the length of described (N-1) individual delay optical fiber is all different, and every two adjacent length differences that postpone between optical fiber are identical.
Further, the shift frequency of a described N acousto-optic modulator is all not identical, and the frequency displacement between every two adjacent acousto-optic modulators is poor identical.
The distributed optical fiber vibration sensing system that the present invention is based on differential pulse sequence adopts differential pulse time series technique, make the burst pulse light signal of a row different frequency successively enter long-distance sensing optical fiber in a short time difference, by being accurately set, delay fiber lengths controls the difference time, N time difference pulse train can realize within a sampling period to be measured N time of vibration event, thereby increase thus sampling number and improve system frequency response, simultaneously, said system adopts heterodyne demodulation method to be conducive to improve restituted signal signal to noise ratio (S/N ratio), can realize simultaneously the high precision of vibration position signal and higher vibration frequency signal is detected.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing;
Fig. 1 is the index path of the first better embodiment that the present invention is based on the distributed optical fiber vibration sensing system of differential pulse sequence.
Fig. 2 is the index path of the second better embodiment that the present invention is based on the distributed optical fiber vibration sensing system of differential pulse sequence.
Specific embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
Should be understood that, although can use the terms such as " first ", " second " to describe various elements herein, these elements should not limited by these terms.These terms are only used for distinguishing an element and another element.Therefore " first " element of, below discussing also can be called as " second " element and not depart from instruction of the present invention.Should be understood that, when mentioning an element " connection " or " connection " to another element, it can directly connect or directly be connected to another element or also can have intermediary element.On the contrary, when mentioning that an element " directly connects " or " directly connecting " arrives another element, there is not intermediary element.
Term is only not intended to as limitation of the invention for describing the object of concrete embodiment as used herein.As used herein, unless context clearly point out in addition, singulative intention also comprises plural form.
It should be further understood that, when using in this manual term " to comprise " and/or when " including ", these terms have indicated the existence of described feature, integral body, step, operation, element and/or parts, but also do not get rid of the existence of above other features, integral body, step, operation, element, parts and/or its group and/or add.
Refer to Fig. 1 and Fig. 2, the better embodiment of a kind of distributed optical fiber vibration sensing system based on differential pulse sequence of the present invention comprises that light source 1, the first coupling mechanism 2, first sound-optic modulator 3 are to N acousto-optic modulator 4, (N-1) individual delay optical fiber 5, the second coupling mechanism 11, Erbium-Doped Fiber Amplifier (EDFA) 7, optical filter 8, three port circulators 9, long-distance sensing optical fiber 10, the 3rd coupling mechanism 6, photodetector 12, Hi-pass filter 13, frequency mixer 14, function generator 15, low-pass filter 16 and data collecting card 17.Wherein, described long-distance sensing optical fiber 10 is layed in detected space.In present embodiment, described the first coupling mechanism 2 is 1 * (N+1) coupling mechanism, and described the 3rd coupling mechanism 6 is N * 1 coupling mechanism, the shift frequency of an above-mentioned N acousto-optic modulator is all not identical, and the frequency displacement between every two adjacent acousto-optic modulators is poor identical, and wherein N is more than or equal to 2 natural number.For ease of describing, two acousto-optic modulators have been shown in Fig. 1, i.e. N=2, now the quantity of described delay optical fiber is one, and described the first coupling mechanism 2 is 1 * 3 coupling mechanism, and described the 3rd coupling mechanism 6 is 2 * 1 coupling mechanisms; Three acousto-optic modulators have been shown in Fig. 2, i.e. N=3, now the quantity of described delay optical fiber is two, and described the first coupling mechanism 2 is 1 * 4 coupling mechanism, and described the 3rd coupling mechanism 6 is 3 * 1 coupling mechanisms.
To respectively Fig. 1 and Fig. 2 be described below:
Please refer again to shown in Fig. 1, described light source 1 is connected with the input end light path of the first coupling mechanism 2, and the first to the 3rd output terminal of described the first coupling mechanism 2 is corresponding to be respectively connected with the input end of first sound-optic modulator 3, second sound-optic modulator 4 and the first input end of the second coupling mechanism 11.The output terminal of described first sound-optic modulator 3 is connected with the first input end of the 3rd coupling mechanism 6, the output terminal of described second sound-optic modulator 4 is connected with the input end that postpones optical fiber 5, and the output terminal of described delay optical fiber 5 is connected with the second input end of the 3rd coupling mechanism 6.
The output terminal of described the 3rd coupling mechanism 6 is connected with the input end of Erbium-Doped Fiber Amplifier (EDFA) 7, the output terminal of described Erbium-Doped Fiber Amplifier (EDFA) 7 is connected with the input end of optical filter 8, the output terminal of described optical filter 8 is connected with the input end of three port circulators 9, the multiplexing end of transmitting-receiving of described three port circulators 9 is connected with the second input end of the second coupling mechanism 11, and the output terminal of described three port circulators 9 is connected with one end of long-distance sensing optical fiber 10.
The output terminal of described the second coupling mechanism 11 is connected with the input end of photodetector 12, the output terminal of described photodetector 12 is connected with the input end of Hi-pass filter 13, the output terminal of described Hi-pass filter 13 is connected with the first input end of frequency mixer 14, the second input end function generator 15 of described frequency mixer 14 is connected, and described function generator 15 is also connected with first sound-optic modulator 3 and second sound-optic modulator 4.The output terminal of described frequency mixer 14 is connected with the input end of low-pass filter 16, and the output terminal of described low-pass filter 16 is connected with data collecting card 17.
Described the first coupling mechanism 2 using input light be divided into three tunnels: first via light as sensed light signal export first sound-optic modulator 3 to, the second road light exports second sound-optic modulator 4, Third Road light to as export the first input end of the second coupling mechanism 11 to reference to light signal as sensed light signal.3 pairs of input light of described first sound-optic modulator carry out exporting light to the 3rd coupling mechanism 6 after modulation treatment, and 4 pairs of input light of second sound-optic modulator export light to postpone optical fiber 5 to after modulating simultaneously.In present embodiment, the light signal shift frequency amount of above-mentioned two acousto-optic modulators is different.Sequentially the light signal via second sound-optic modulator 4 and 5 outputs of delay optical fiber has the delay of a short time with respect to the light signal via described first sound-optic modulator 3 outputs.These two light signals with a timing difference are all input to the 3rd coupling mechanism 6, and after the 3rd coupling mechanism 6 coupling processings, light signal is input to Erbium-Doped Fiber Amplifier 7 to amplify processing.Afterwards, the light signal being amplified after processing is input to optical filter 8 and carries out denoising Processing.Optical signals optical filter 8 after denoising Processing transfers to three port circulators 9, and described three port circulators 9 are for the backward Rayleigh scattering light of the detection light signal generating extracting long-distance sensing optical fiber 10 and produced by two acousto-optic modulators.
Afterwards, the backward Rayleigh scattering signal that the detection light signal being produced by two acousto-optic modulators respectively produces is taken up in order of priority and in the second coupling mechanism 11, beat frequency interference is occurred with reference optical signal.Described Hi-pass filter 13 for extract sensed light signal and reference signal interference signal exchange phase, described frequency mixer 14 carries out mixing for the cosine signal that phase function generator 15 exports that exchanges to the interference signal of detection signal and reference signal in frequency mixer 14.Described low-pass filter 16 for filtering from the high frequency noise in the signal of frequency mixer 14 to obtain down-conversion signal, Rayleigh scattering signal after described data collecting card 17 is reconciled for serial acquisition, the Rayleigh scattering signal collecting can be used for follow-up analytical calculation.
To the principle of work of the above-mentioned distributed optical fiber vibration sensing system based on differential pulse sequence be elaborated below:
The light of being exported by described light source 1 is divided into three-beam by the first coupling mechanism 2, wherein two bundles are modulated to respectively the first burst pulse light signal and the second narrow pulse signal by first sound-optic modulator 3 and second sound-optic modulator 4 respectively as detecting light, wherein, the second narrow pulse signal has the pulse pair of poor different frequency of a short time after one section of delay optical fiber 5 with the first narrow pulse signal formation one, described pulse is carried out light amplification to entering Erbium-Doped Fiber Amplifier (EDFA) 7 by the 3rd coupling mechanism 6, light signal injects long-distance sensing optical fiber 10 by three port circulators 9 subsequently, and in long-distance sensing optical fiber 10, inspire respectively two and have the rear to Rayleigh scattering light of poor different frequency of a short time, when extraneous vibration acts on long-distance sensing optical fiber 10, will cause that within the scope of light impulse length, the phase place of backward Rayleigh scattering light changes, article two, there are Rayleigh back scattering and the reference light of poor different frequency of a short time, at the second coupling mechanism 11 places, beat frequency interference occurs, photodetector 12 just gathers the backward Rayleigh scattering light beat frequency from the output terminal of the second coupling mechanism 11 at interval of some cycles, in each collection period, can collect the back scattering light signal of two different frequencies, two scattered light signals are because frequency is not identical so aliasing can not occur, and by envelope detection method, two scattered light signals can be distinguished in computing machine, after a plurality of sampling periods, can collect a large amount of scattered signals, because two separated scattered signals have a short time poor, according to sampling time sequencing, arrange all sampling scattered signals, and long-distance sensing optical fiber 10 positions that guarantee sampling scattered signal are corresponding one by one, the scattered signal arranging is done to moving average and mobile difference processing, can draw the positional information of vibration.Take out the time-domain signal of vibration position, it is done to the frequency information that Nonuniform fast Fourier transform can draw vibration.
In order to improve the signal to noise ratio (S/N ratio) of the signal that described the second coupling mechanism 11 exports, in present embodiment, described photodetector 12 adopts balance photodetector, described the second coupling mechanism 11 adopts 2 * 2 coupling mechanisms, and two output terminals of described the second coupling mechanism 11 are connected one by one with two input ends of photodetector 12.In addition, the frequency that described function generator 15 connects the first port of first sound-optic modulators 3 and connects the electric impulse signal that the second port of second sound-optic modulator 4 produces is 80KHz, pulsewidth and is that 100ns, high level amplitude are 1V, low level amplitude is 0V, and described function generator 15 is consistent to the driving parameter of first and second acousto-optic modulator; The length of described delay optical fiber 5 is 120 meters, and the frequency of the cosine signal that the 3rd port that described function generator 15 connects frequency mixer 14 produces is 85MHz.
Please refer again to shown in Fig. 2, in order to save the length of word, to only both differences be described below, the difference of itself and Fig. 1 is also to comprise that the 3rd acousto-optic modulator 40 and another postpone optical fiber 50, and first to fourth output terminal of described the first coupling mechanism 2 is corresponding to be respectively connected with the input end of first sound-optic modulator 3, second sound-optic modulator 4, the 3rd acousto-optic modulator 40 and the first input end of the second coupling mechanism 11.The output terminal of described first sound-optic modulator 3 is connected with the first input end of the 3rd coupling mechanism 6, the output terminal of described second sound-optic modulator 4 and the 3rd acousto-optic modulator 40 is corresponding to be respectively connected with the input end that postpones optical fiber 5 and 50, and described delay optical fiber 5 and 50 output terminal respectively correspondence are connected with second and third input end of the 3rd coupling mechanism 6.Described function generator 15 is also connected with first sound-optic modulator 3, second sound-optic modulator 4 and the 3rd acousto-optic modulator 40.
Described the first coupling mechanism 2 is divided into four tunnels using input light: first via light as sensed light signal export to first sound-optic modulator 3, the second road light as sensed light signal export second sound-optic modulator 4 to, Third Road light exports the 3rd acousto-optic modulator 40, Si road light to as export the first input end of the 3rd coupling mechanism 11 to reference to light signal as sensed light signal.3 pairs of input light of described first sound-optic modulator carry out exporting light to second coupling mechanism 6 after modulation treatment, and second sound-optic modulator 4 and the 3rd acousto-optic modulator 40 export light correspondence to postpone optical fiber 5 and 50 to after respectively input light being modulated simultaneously.In present embodiment, the light signal shift frequency amount of each acousto-optic modulator in above-mentioned three acousto-optic modulators is all different, and the frequency displacement between every two adjacent acousto-optic modulators is poor identical; Above-mentioned two length that postpone optical fiber are also not identical.Sequentially the light signal via second sound-optic modulator 4 and 5 outputs of delay optical fiber has the delay of a short time with respect to the light signal via described first sound-optic modulator 3 outputs, and the light signal of sequentially exporting via the 3rd acousto-optic modulator 40 and delay optical fiber 50 is with respect to sequentially have the delay of a short time via the light signal of described second sound-optic modulator 4 and 5 outputs of delay optical fiber.These three light signals with a timing difference are all input to the second coupling mechanism 6, and after the second coupling mechanism 6 coupling processings, light signal is input to Erbium-Doped Fiber Amplifier 7 to amplify processing.Afterwards, the light signal being amplified after processing is input to optical filter 8 and carries out denoising Processing.Optical signals optical filter 8 after denoising Processing transfers to three port circulators 9, and described three port circulators 9 are for the backward Rayleigh scattering light of the detection light signal generating extracting long-distance sensing optical fiber 10 and produced by three acousto-optic modulators.
Afterwards, the backward Rayleigh scattering signal that the detection light signal being produced by three acousto-optic modulators respectively produces is taken up in order of priority and in the second coupling mechanism 11, beat frequency interference is occurred with reference optical signal.Described Hi-pass filter 13 for extract sensed light signal and reference signal interference signal exchange phase, described frequency mixer 14 carries out mixing for the cosine signal that phase function generator 15 exports that exchanges to the interference signal of detection signal and reference signal in frequency mixer 14.Described low-pass filter 16 for filtering from the high frequency noise in the signal of frequency mixer 14 to obtain down-conversion signal, Rayleigh scattering signal after described data collecting card 17 is reconciled for serial acquisition, the Rayleigh scattering signal collecting can be used for follow-up analytical calculation.
The distributed optical fiber vibration sensing system that the present invention is based on differential pulse sequence adopts differential pulse time series technique, make the burst pulse light signal (being differential pulse series) of N different frequency successively enter long-distance sensing optical fiber in a short time difference, the length that postpones optical fiber by accurately arranging is controlled the difference time, N time difference pulse signal can be realized the repeatedly measurement to vibration event within a sampling period, thereby increase thus sampling number, improves system frequency response.Meanwhile, whole distributed optical fiber vibration sensing system adopts heterodyne demodulation method, is conducive to improve the signal to noise ratio (S/N ratio) of restituted signal.The above-mentioned distributed optical fiber vibration sensing system based on differential pulse sequence can be realized simultaneously the high precision of vibration position signal and higher vibration frequency signal is detected.
Certainly, in other embodiments, the quantity of described acousto-optic modulator can be more, as long as it is more than or equal to two, corresponding, the quantity of described delay optical fiber also will increase, few one than the quantity of acousto-optic modulator of the quantity of wherein said delay optical fiber.Meanwhile, the specification of described the first coupling mechanism and the 3rd coupling mechanism is also wanted correspondence adjustment.To sum up, the distributed optical fiber vibration sensing system that the present invention is based on differential pulse sequence comprises that light source, the first coupling mechanism, first are to N acousto-optic modulator, (N-1) individual delay optical fiber, the second coupling mechanism, Erbium-Doped Fiber Amplifier (EDFA), optical filter, three port circulators, long-distance sensing optical fiber, the 3rd coupling mechanism, photodetector, Hi-pass filter, frequency mixer, function generator, low-pass filter and data collecting card.Wherein, described the first coupling mechanism is 1* (N+1) coupling mechanism, described the 3rd coupling mechanism is N*1 coupling mechanism, the shift frequency of an above-mentioned N acousto-optic modulator all frequency displacement between not identical and every two adjacent acousto-optic modulators is poor identical, the equal difference of length of above-mentioned (N-1) individual delay optical fiber and every two adjacent length differences that postpone between optical fiber are identical, and wherein N is more than or equal to 2 natural number.
Described light source is connected with the input end light path of the first coupling mechanism, first of described the first coupling mechanism is connected with the first input end to N acousto-optic modulator to N output terminal is corresponding respectively, and (N+1) output terminal of described the first coupling mechanism is connected with the first input end of the second coupling mechanism.The output terminal of described first sound-optic modulator is connected with the first input end of the 3rd coupling mechanism, described the second output terminal to N acousto-optic modulator is respectively corresponding to be connected with the input end of (N-1) individual delay optical fiber, and the output terminal of described (N-1) individual delay optical fiber is distinguished second of corresponding and the 3rd coupling mechanism and is connected to N input end.
Described the 3rd output terminal of coupling mechanism and the input end of Erbium-Doped Fiber Amplifier (EDFA) are connected, the output terminal of described Erbium-Doped Fiber Amplifier (EDFA) is connected with the input end of optical filter, the output terminal of described optical filter is connected with the input end of three port circulators, the multiplexing end of transmitting-receiving of described three port circulators is connected with the second input end of the second coupling mechanism, and the output terminal of described three port circulators is connected with one end of long-distance sensing optical fiber.
The output terminal of described the second coupling mechanism is connected with the input end of photodetector, the output terminal of described photodetector is connected with the input end of Hi-pass filter, the output terminal of described Hi-pass filter is connected with the first input end of frequency mixer, the second input end function generator of described frequency mixer is connected, and described function generator is also all connected to N acousto-optic modulator with first.The output terminal of described frequency mixer is connected with the input end of low-pass filter, and the output terminal of described low-pass filter is connected with data collecting card.
Above disclosed is only a kind of preferred embodiment of the present invention, certainly can not limit with this interest field of the present invention, and the equivalent variations of therefore doing according to the claims in the present invention, still belongs to the scope that the present invention is contained.
Claims (9)
1. the distributed optical fiber vibration sensing system based on differential pulse sequence, for the vibration of designated space is carried out to sensing, is characterized in that: the described distributed optical fiber vibration sensing system based on differential pulse sequence comprises:
Light source (1), the first coupling mechanism (2), first sound-optic modulator (3) are to N acousto-optic modulator, (N-1) individual delay optical fiber, the second coupling mechanism (11), Erbium-Doped Fiber Amplifier (EDFA) (7), optical filter (8), three port circulators (9), long-distance sensing optical fiber (10), the 3rd coupling mechanism (6), photodetector (12), Hi-pass filter (13), frequency mixer (14), function generator (15), low-pass filter (16) and data collecting card (17), and wherein N is more than or equal to 2 natural number; described long-distance sensing optical fiber (10) is layed in tested designated space, described light source (1) is connected with the input end light path of the first coupling mechanism (2), first of described the first coupling mechanism (2) is connected with the first input end to N acousto-optic modulator respectively to N output terminal, (N+1) output terminal of described the first coupling mechanism (2) is connected with the first input end of the second coupling mechanism (11), the output terminal of described first sound-optic modulator (3) is connected with the first input end of the 3rd coupling mechanism (6), the output terminal of described second sound-optic modulator to the N acousto-optic modulator is corresponding to be respectively connected with the input end of (N-1) individual delay optical fiber, the output terminal of described (N-1) individual delay optical fiber is second being connected to N input end of corresponding and the 3rd coupling mechanism (6) respectively, the output terminal of described the 3rd coupling mechanism (6) is connected with the input end of Erbium-Doped Fiber Amplifier (EDFA) (7), the output terminal of described Erbium-Doped Fiber Amplifier (EDFA) (7) is connected with the input end of optical filter (8), the output terminal of described optical filter (8) is connected with the input end of three port circulators (9), the multiplexing end of transmitting-receiving of described three port circulators (9) is connected with the second input end of the second coupling mechanism (11), the output terminal of described three port circulators (9) is connected with one end of long-distance sensing optical fiber (10), the output terminal of described the second coupling mechanism (11) is connected with the output terminal of photodetector (12), the output terminal of described photodetector (12) is connected with the input end of Hi-pass filter (13), the output terminal of described Hi-pass filter (13) is connected with the first input end of frequency mixer (14), the second input end function generator (15) of described frequency mixer (14) is connected, described function generator (15) is also connected with second sound-optic modulator (4) with first sound-optic modulator (3), the output terminal of described frequency mixer (14) is connected with the input end of low-pass filter (16), the output terminal of described low-pass filter (16) is connected with data collecting card (17).
2. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: described the first coupling mechanism is 1 * and (N+1) coupling mechanism.
3. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: described the 3rd coupling mechanism is N * 1 coupling mechanism.
4. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: described photodetector (12) is balance photodetector.
5. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 4, it is characterized in that: described the second coupling mechanism (11) is 2 * 2 coupling mechanisms, two output terminals of described the second coupling mechanism (11) are connected one by one with two input ends of balance photodetector.
6. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: described function generator (15) is consistent to the driving parameter of N acousto-optic modulator to first.
7. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: the frequency of the cosine signal that the 3rd port of described function generator (15) connection frequency mixer (14) produces is 85MHz.
8. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: the length of described (N-1) individual delay optical fiber is all different, and every two adjacent length differences that postpone between optical fiber are identical.
9. the distributed optical fiber vibration sensing system based on differential pulse sequence as claimed in claim 1, is characterized in that: the shift frequency of a described N acousto-optic modulator is all not identical, and the frequency displacement between every two adjacent acousto-optic modulators is poor identical.
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| CN104457962A (en) * | 2014-12-25 | 2015-03-25 | 上海远洲管业科技股份有限公司 | Super-long-distance distributed type optical fiber vibration sensing monitoring system |
| CN104457960A (en) * | 2014-12-11 | 2015-03-25 | 中国科学院半导体研究所 | Distributed optical fiber sensing system based on coherent reception technology |
| CN104568120A (en) * | 2015-01-14 | 2015-04-29 | 天津大学 | Composite principle optical fiber sensing system and sensing method |
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| CN111207821A (en) * | 2020-01-19 | 2020-05-29 | 国兴汇金(深圳)科技有限公司 | Optical fiber distributed vibration sensing system with adjustable gauge length |
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| CN107894276A (en) * | 2017-12-08 | 2018-04-10 | 威海北洋光电信息技术股份公司 | The distributed optical fiber vibration sensing device and implementation method of a kind of high frequency sound |
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| CN114111860A (en) * | 2021-12-03 | 2022-03-01 | 北京科技大学 | Distributed phi-OTDR sensing method and system based on multi-frequency pulse coding |
| CN114111860B (en) * | 2021-12-03 | 2022-08-30 | 北京科技大学 | Distributed phi-OTDR sensing method and system based on multi-frequency pulse coding |
| CN116772908A (en) * | 2021-12-28 | 2023-09-19 | 西安和其光电科技股份有限公司 | Signal data processing method applied to distributed optical fiber acoustic wave sensing system |
| CN114353931A (en) * | 2022-01-12 | 2022-04-15 | 中国人民解放军国防科技大学 | Phase detection device and method for optical fiber interferometer with large dynamic range |
| CN114459593A (en) * | 2022-01-25 | 2022-05-10 | 北京信维科技股份有限公司 | Method for increasing detection distance of optical fiber vibration system |
| CN114459593B (en) * | 2022-01-25 | 2024-01-30 | 北京信维科技股份有限公司 | Method for improving detection distance of optical fiber vibration system |
| CN116073900A (en) * | 2023-03-28 | 2023-05-05 | 中山大学 | Distributed optical fiber acoustic wave sensing system and blind area elimination detection method |
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